1. Field of the Invention
The present invention relates to a servo amplifier that is utilized for controlling the speed of a DC motor. More specifically, the present invention is directed to improvements in sub-circuits of the servo amplifier, including the provision of easily accessible resistance and potentiometer adjustments, high speed response to changes in the desired speed and in the response of the servo amplifier without hunting or over-shoot and a start-up delay circuit.
2. Description of the Prior Art:
Heretofore, servo amplifiers have been used in a number of environments for controlling the speed of a DC servo motor in response to a signal related to a desired speed. Examples of such servo amplifiers or servo electronic circuits are disclosed in the following U.S. Patents:
______________________________________ U.S. Pat. No. Patentee ______________________________________ 3,866,246 Seamone et al. 4,039,917 Bach et al. 4,081,731 Wesner 4,146,828 Ross et al. 4,204,143 Coleman 4,803,410 Shinohara et al. ______________________________________
The Seamone et al. U.S. Pat. No. 3,866,246 discloses a triangular wave generator and a pulse width modulator which are coupled to a power switching transistor circuit.
The Bach et al. U.S. Pat. No. 4,039,917 discloses an on-off servo controller generating a pulse-duration-modulated, error-compensating signal and includes a time delayed feedback voltage circuit.
The Wesner U.S. Pat. No. 4,081,731 discloses a pulse width modulated servo amplifier with over-current protection.
The Ross et al. U.S. Pat. No. 4,146,828 discloses a pulse-modulated servo amplifier.
The Coleman U.S. Pat. No. 4,204,143 discloses a pulse width modulated power amplifier direct current motor control.
The Shinohara et al. U.S. Pat. No. 4,803,410 discloses at variable duty ratio speed controller for DC motor.
As will be described in greater detail hereinafter, the servo amplifier of the present invention differs from the servo amplifiers disclosed in the patents referred to above by providing novel tri-state logic drive circuitry for effecting fast response of the servo amplifier to a change in the signal related to the desired speed, and more specifically, to the error signal generated thereby and fast response of the DC motor from its present speed to the desired speed with no over-shoot, or hunting.
Also, the servo amplifier of the present invention provides user adjustable controls for resistances and voltages in the circuit which are mounted for easy access to a user of the servo amplifier. Still further, the servo amplifier of the present invention includes a start-up delay circuit.